1. Field of the Invention
The present invention generally relates to membrane materials and systems for selective removal of specified gases and, more particularly, to a gas separation membrane which employs a zeolite material.
2. Description of the Prior Art
Membrane separations represent a growing technological area with potentially high economic reward, due to low energy requirements and facile scale-up of membrane modular design. Advances in membrane technology, especially in novel membrane materials, will make this technology even more competitive with traditional, high-energy intensive and costly processes such as low temperature distillation and adsorption. In particular, there is need for large-scale gas separation membrane systems, which could handle processes such as nitrogen enrichment, oxygen enrichment, hydrogen recovery, acid gas (CO2, H2S) removal from natural gas and dehydration of air and natural gas, as well as various hydrocarbon separations. Materials employed in these applications must have durability, productivity and high separation performance if they are to be economically viable. Currently, polymers and certain inorganic membranes are the only candidates.
While inorganic membranes have permselectivities that are five times to ten times higher than traditional polymeric materials and moreover are more stable in aggressive feeds, they are not economically feasible for large-scale applications. Most ceramic, glass, carbon and zeolitic membranes cost between one- and three-orders of magnitude more per unit of membrane area when compared to polymeric membranes and furthermore are difficult to fabricate into large, defect-free areas. An advantage of polymeric materials is that they can be processed into hollow fibers, which offer high separation productivity due to the inherently high surface area to volume ratio. Thus, most commercially available gas separating membranes are still made from polymers despite the limited membrane performance.